This invention relates to an electrical alternator for use on a boat. Specifically, the invention relates to a compact, low drag alternator to be used on a high speed boat for charging batteries.
Modern bass fishing boats are very sophisticated, high performance water craft. They are designed to provide the maximum amount of fishing time in a day. Bass fishing tournaments are popular events, often with large monetary prizes to the winner of the tournament. Therefore, bass fishermen are willing to pay large amounts of money for an optimized boat that can give them a competitive advantage in tournaments.
Typical bass fishing boats are designed to go from the dock to the fishing location as quickly as possible, and then to slowly troll at the fishing location using an electric trolling motor. To go to the fishing location quickly, they have a sleek, hydrodynamic hull and a powerful outboard gasoline engine. Often the boats will have engines approaching 300 horsepower, and are capable of traveling at speeds up to 80 miles per hour. Once at the fishing location, such a high powered engine is clearly not needed. The large gasoline powered outboard motors used on bass fishing boats are usually not capable of propelling the boat at the slow speeds required for trolling. Also, the noise from the gasoline engine generally scares the fish away and is detrimental to fishing success. Therefore, all bass fishing boats are equipped with a small auxiliary trolling motor. The auxiliary trolling motor is usually electrically powered and very quiet.
In order to power the electrical trolling motor it is necessary to carry a bank of batteries on the boat. The amount of time that can be spent fishing is often limited by the energy available in the batteries. Once the batteries have been depleted, it is not possible to use the trolling motor and the day of fishing is over. So while fishermen are willing to spend large amounts of money for a high performance boat and engine to get them to and from their fishing location, the actual time that they can spend fishing is often limited by the electrical energy available for their small trolling motor.
The only way to extend the charge time of the batteries for the trolling motor is to carry extra batteries. Because batteries are large and heavy, it is not practical to carry more than 4 or 5 batteries. Most boats carry 3 batteries. When the batteries on board the boat are depleted, it is necessary to return to the dock to recharge the batteries, or at least to swap out the batteries for a fresh set. During a fishing tournament, this lost fishing time for charging or exchanging the batteries could mean the difference between winning or losing the tournament. Therefore, it would be desirable to provide a method of charging the batteries for the trolling motor during a fishing trip without the need to return to the dock.
Alternators are commercially available on the drive train of the large gasoline powered outboard engine for bass fishing boats. However, the available alternators are only intended to provide electrical energy to charge the starting battery and for operating onboard electrical equipment such as radios, lights, and miscellaneous electronic instrumentation. The available alternators are generally not big enough to adequately charge the batteries for the trolling motor. Most boats have only a 24 amp alternator, whereas a 45-60 amp alternator would be required to adequately charge the trolling batteries. Furthermore, the latest trolling motors operate on a 24 to 48 VDC electrical system, whereas the alternators found in all outboard engines are only capable of charging a 12 VDC electrical system.
Several battery chargers are described in the prior art. The prior art battery chargers are not suitable for use on high performance, high speed bass fishing boats. The prior art includes several battery charging alternators that are powered by a propeller. However, the prior art devices are designed for use on slow moving boats such as sail boats or low powered motor boats. The prior art devices are characterized by relatively large, slow turning propellers. The prior art devices would cause unreasonable drag forces on the boat when traveling at high speed. Also, the prior art devices all utilize direct current generators. DC generators are generally not well suited for use in a hydro-alternator on a fast moving boat because they tend to be large and relatively inefficient.